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. 2020 Feb 3:13:323-332.
doi: 10.2147/IDR.S238811. eCollection 2020.

Prevalence and Some Possible Mechanisms of Colistin Resistance Among Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa

Rehab M Abd El-Baky  1   2 , Salwa M Masoud  1 , Doaa S Mohamed  2 , Nancy Gfm Waly  1 , Engy A Shafik  3 , Dina A Mohareb  4 , Azza Elkady  5 , Mohamed M Elbadr  6 , Helal F Hetta  7   8
Affiliations

Prevalence and Some Possible Mechanisms of Colistin Resistance Among Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa

Rehab M Abd El-Baky et al. Infect Drug Resist. .

Abstract

Background and aim: The emergence of colistin-resistant strains is considered a great threat for patients with severe infections. Here, we investigate the prevalence and some possible mechanisms of colistin resistance among multidrug-resistant (MDR) and extensively drug-resistant (XDR) Pseudomonas aeruginosa (P. aeruginosa).

Methods: Antimicrobial susceptibility was performed using disc diffusion methods while colistin resistance was detected by agar dilution method. Possible mechanisms for colistin resistance were studied by detection of mcr-1 and mcr-2 genes by conventional PCR, detection of efflux mechanisms using Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP), studying outer membrane protein profile and Lipopolysaccharide (LPS) profile of resistant isolates.

Results: It was found that MDR and XDR represented 96% and 87% of the isolated P. aeruginosa, respectively, and colistin resistance represented 21.3%. No isolates were positive for mcr-2 gene while 50% of colistin-resistant isolates were positive for mcr-1. Efflux mechanisms were detected in 3 isolates. Protein profile showed the presence of a band of 21.4 KDa in the resistant strains which may represent OprH while LPS profile showed differences among colistin-resistant mcr-1 negative strains, colistin-resistant mcr-1 positive strains and susceptible strains.

Conclusion: The current study reports a high prevalence of colistin resistance and mcr-1 gene in P. aeruginosa strains isolated from Egypt that may result in untreatable infections. Our finding makes it urgent to avoid unnecessary clinical use of colistin.

Keywords: MDR; Pseudomonas aeruginosa; XDR; colistin resistance; mcr-1; mcr-2; toxA gene.

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Conflict of interest statement

The authors report no conflicts of interest in this work.

Figures

Figure 1
Figure 1
Antibiotic resistance pattern of all isolated P. aeruginosa isolates.
Figure 2
Figure 2
Phenotypic detection for mcr positive isolates by combined disc diffusion test (CDT). (A): mcr-1 positive strain showed an increase in the zone diameter of discs with colistin and EDTA ≥ 3mm in comparison to colistin alone. (B): mcr-1 negative isolate showed slight change (1 mm) in the inhibition zone diameter of colistin and EDTA disc in comparison to colistin alone.
Figure 3
Figure 3
Antibiotic resistance pattern of colistin-resistant isolates.
Figure 4
Figure 4
Outer membrane SDS-PAGE of colistin resistant and sensitive strains. Lane 1: Protein Marker, Lane 2 and Lane 3: colistin-resistant strains (P1 & P12), Lanes 4–6: colistin sensitive strains.
Figure 5
Figure 5
LPS bands pattern. Lanes 1, 2 & 3: colistin-resistant mcr-1 negative strains (P3, P6 & P10, respectively), Lane 4: Colistin sensitive strains and Lane 5: Colistin-resistant mcr-1 positive strain (P1). O-antigen repeats are boxed and arrow refers to LPS core.
See this image and copyright information in PMC

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